IMAGE DESCRIPTION:
The Earth's diameter is roughly 8000 miles, the troposphere (AKA survivable layer where the bulk of the atmosphere is located) is roughly 5-9 miles in thickness --for our purposes, let's high-side it and go with 9 miles. If we take the radius value, assume a scale of 1/16":1 mile that comes out to 9/16" representational troposphere thickness and, starting at the earth/air boundary, puts the Earth's geometric center roughly 20'10" away. IMAGE DEMONSTRATING SPREAD, REACH OF HUMANITY. If the raw numbers are too abstract, get out a tape measure and lay out the distances. Now consider the illustration of humanity's spread and the fact that Earth's atmosphere is a finite quantity.
